A click-to-chat link is the simplest opt-in to collect at a fair. The buyer scans, the chat opens with your message already typed, and they press Send. Because they wrote first, the 24-hour customer window is open, and your reply, samples list included, needs no template.
French makes the link longer than it looks. Each accented letter turns into six characters, so a short sentence with a handful of accents grows quickly, and a longer link prints as a denser QR code on a business card. Keep the pre-fill to one line, put the detail in your reply, and test the printed code on a phone before the fair opens.
The number in the link is digits only, country code first, with no + or spaces. The conversation that follows can run from the shared team inbox, and your order system can send the updates through the developer API.